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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

At least 109 records · Page 6Linked to original sources
PubMed1993

[The marginal adaptation and wear resistance of a fine hybrid composite inlay in vitro].

A lab and a production batch of a new fine hybrid composite material were tested in adhesive MOD inlays. Using a long term in vitro test the wear resistance of both formulations and the marginal adaptation of the production batch were quantitated. The wear results were compared to the results generated with an amalgam control. The initial marginal adaptation in enamel was excellent totaling 95.9% (occlusal) to 99.5% (axial) of "continuous margin" at the tooth/cement interface. These values slightly decreased after loading to 81.4% (occlusal) and 93.8% (axial), respectively. In dentine however, insufficient marginal qualities were found (32.0% "continuous margin" initial and 18.9% after loading). The adhesion between inlay and composite cement was excellent and load stable. Both composite batches were significantly more wear resistant than the amalgam control and abraded the opposing enamel cusps significantly less than amalgam.

Composite Resins↗
PubMed1993

Self-adjusting abrasiveness: a new technology for prophylaxis pastes.

An ideal prophylaxis paste should have both cleaning and polishing properties. Key elements would be abrasive particles that become less aggressive under load. The abrasive perlite, a volcanic glass with a sheetlike geometry, is claimed to have these unique properties. This study evaluated the average particle size, size distribution, and morphology of perlite in raw form, in an unused prophylaxis paste, and a used prophylaxis paste. The surface roughness induced on enamel and dentinal specimens was quantitated after paste application in either a rubber cup or a nylon brush. Flour of pumice, a standard prophylaxis paste, a polishing paste, and water were tested similarly. The luster induced by the tested pastes and controls was assessed. Perlite blunted and disintegrated under load. The perlite-containing prophylaxis paste acted as a fine or superfine prophylaxis paste, although it was ranked as medium, based on the mean particle size of its abrasive in the fresh, unused form. Perlite might provide the properties required for the abrasive material of an ideal prophylaxis paste.

Aluminum Oxide↗
PubMed1993

Comparison of the efficacy of prophylaxis pastes with conventional abrasives or a new self-adjusting abrasive.

A newly developed prophylaxis paste that contains perlite as an abrasive medium (Cleanic) was compared to conventional prophylaxis pastes with regard to relative dentin and enamel abrasion, cleaning ability, and polishing power. Rubber cups and nylon brushes were used as paste carriers. Water, flour of pumice, and the dentin-polishing paste CCS 40 served as controls. The tested prophylaxis pastes, selected according to their popularity among clinicians, were CCS 250, Détartrine Z, Nupro Coarse, and Zircate. The Prophylaxis Paste Index was created to assess the clinical potential of the various prophylaxis pastes more accurately. The Index was computed for dentin as cleaning ability dended by relative dentin abrasion x surface roughness (in Ra) x 10, and for enamel as cleaning ability dended by relative enamel abrasion x surface abrasion (in Ra). On dentin and enamel, Cleanic consistently yielded low relative dentin and enamel abrasion values, a good cleaning ability, and low surface roughness scores with both rubber cups and nylon brushes. Of all tested prophylaxis pastes, Cleanic excelled in the Prophylaxis Paste Index on dentin and enamel and with both rubber cup and nylon brush applications. Therefore, a perlite-containing prophylaxis paste has broad professional therapeutic indications and may be used universally as a single paste to clean and polish both dentin and enamel.

Aluminum Oxide↗
PubMed1993

[Pharmacotherapy 100 years ago].

In the second part of the 19th century experiments in the sciences, in particular in pharmacology, formed the rational understanding of the present pharmacotherapy. The industry in beginning developed techniques for synthetic pharmaceutical products. A literature study shows that 100 years ago was the time in which the veterinarians get at first the possibility to work with synthetic antiinfective, antipyretic, laxative and anesthetic drugs.

Drug Therapy↗
PubMed1993

[Adhesive systems for tooth-colored restorations. A review].

The quality, longevity and the esthetic appearance of tooth-colored restorations are primarily dependent upon the integrity of the bond of the restoration with the enamel and dentin. Consequently, the enamel and dentin adhesives which are increasingly combined in the so-called adhesive systems play key roles in restorative dentistry. This paper describes the components, the clinical technique, the importance of the systems and the relevant adhesive mechanisms.

Chemical Phenomena↗
PubMed1992

Site-directed mutagenesis of the Pseudomonas aeruginosa cytotoxin for probing toxic activity.

The location of amino acids with direct influence on toxic activity in the pore-forming cytotoxin from Pseudomonas aeruginosa was tested by site-directed mutagenesis. Mutant fragments obtained by the polymerase-chain reaction were subcloned into a cytotoxin gene-bearing plasmid to minimize the possibility of amplification error. Our data suggest an important role of cysteines for toxic activity of cytotoxin. Furthermore, domain-facilitating-binding to plasma membranes is located on the C-terminal side of Cys215.

Bacteriophages↗
PubMed1992

Schistosoma mansoni: stage-dependent formation and repair of membrane pores induced by a cytotoxin from Pseudomonas aeruginosa.

Various stages of Schistosoma mansoni were treated with a cytotoxin from Pseudomonas aeruginosa and their response to the damaging effect was studied in detail. Marker release and membrane potential measurements showed that the cytotoxin formed stable pores in all developmental stages. However, in juvenile 27-day-old worms, which are refractory to the killing effect of the cytotoxin, the pores had a smaller functional diameter as compared to other stages including 31-day-old worms. Furthermore, these resistant 27-day-old worms, but not susceptible older juvenile worms were able to repair the membrane lesions as shown by restoration of the resting membrane potential. In contrast, older juvenile and adult parasites were unable to cope with the breakdown of the resting potential induced by the cytotoxin. The results demonstrate the existence in 27-day-old schistosomes of effective repair mechanisms dealing with damage to the surface membrane.

Animals↗
PubMed1992

A critical comparison of dentifrice abrasion scores on dentine recorded by gravimetric and radiotracer methods.

Dentifrice abrasivity on dentine is conventionally ranked by various in vitro methods. The abrasivity of selected dentifrices in Switzerland was ranked in 1985 by the gravimetric and in 1989 by the radiotracer method. Because same-named brands of dentifrices were differently ranked by these methods, Swiss clinicians were unsure which ranking to follow. This paper lists the errors known to occur in both techniques, but unfortunately it is difficult to quantitate the magnitudes of these errors. Consequently, it is impossible to determine which method yields the more reliable results. Thus, researchers should look into the problem of dentifrice abrasion scores and try to formulate tests which could simplify the selection of brand-named dentifrices by clinicians and the consumers.

Densitometry↗
PubMed1992

Human root caries: histopathology of arrested lesions.

The histopathology of arrested root caries lesions was examined in extracted human teeth. The main structural characteristics of arrested lesions were the completely mineralized surface area and the formation of a distinct sclerosis of the dentinal tubules. Intertubular dentin was, with the exception of the dentinal tubules, fully mineralized up to the surface. Dentinal tubules near the surface were either filled with ghosts of microorganisms or with crystals of different shapes. Sclerosis of the dentinal tubules was characterized by the presence of three different patterns of intratubular mineralization that occur in distinct regions of the zone of tubular sclerosis. The patterns were distinguishable by the type of crystals and their association with organic structures such as collagenous fibrils or odontoblast processes. It is suggested that arrested lesions are based on (1) the formation of an inner barrier that interrupts the diffusion of substrata from the pulp to invaded bacteria, (2) the formation of an outer barrier by a compact, highly mineralized surface region which blocks the diffusion of products of bacterial metabolism into dentin, and (3) an area of mineralization which extends from the outer barrier toward the root canal within demineralized dentin. The present study demonstrates the considerable potential of caries lesions in dentin to become arrested, and subsequently partially remineralized. These phenomena seem to depend on the severity of an active lesion and its location on the root surface. This should be taken into account when diagnosing root caries lesions. The potential of root caries lesions to become arrested indicates that the treatment concept of active root caries lesions should be reconsidered.

Adult↗
PubMed1992

Effect of contact area size on enamel and composite wear.

The effect of contact area dimensions on the wear of composite specimens and their opposing enamel cusps was evaluated in vitro. Thirty-six standardized cylindrical composite specimens were placed into metal cavities (8 mm x 2 mm) and divided randomly into five groups. The composite used was a fine-particle hybrid and was stressed as follows: storage in 75% aqueous ethanol solution for 24 h, toothbrush/toothpaste-abrasion for 30 min, followed by 300 thermal cycles in water ranging from 5 degrees to 55 degrees C and simultaneous 120,000 occlusal chewing loads at a frequency of 1.7 Hz at 53 N maximum force. In group 1 (n = 12), the occlusal chewing loads were applied by palatal cusps of extracted human maxillary molars with natural morphology. In groups 2 to 5 (n = 6), the cusp tips had standardized contact area dimensions of 0.26, 0.38, 1.18, and 4.10 mm2, respectively. Wear of composite specimens and antagonistic enamel cusps (means +/- SD) was assessed in microns by means of a 3-D scanner. Additionally, the contact surfaces of the restorations and of the antagonistic enamel cusps were evaluated by SEM. Increases in enamel contact areas after being loaded were measured by means of a digitizer and expressed in percent of the initial size before stress exposure. The wear of the composite specimens varied from 69.8 +/- 19.9 to 9.5 +/- 3.6 microns, and that of antagonistic enamel cusps from 31.3 +/- 3.4 to 8.8 +/- 1.5 microns. The increase in contact area varied between 27.8 and 0.1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Cold Temperature↗
PubMed1992

Chewing pressure vs. wear of composites and opposing enamel cusps.

The effects of various chewing pressures on the wear of composites and enamel were assessed in vitro. Standardized composite discs (8 mm in diameter, 2 mm in height) were made of a fine-particle hybrid (FPH), a coarse-particle hybrid (CPH), and a homogeneous microfilled composite (HMC). The composite specimens were chemically degraded by immersion in 75% ethanol for 24 h, brushed for 30 min, and then thermocycled 300 times (5-55-5 degrees C) while being occlusally loaded 120,000 times at 1.7 Hz, with chewing forces of 25, 50, 75, and 100 N. Standardized human enamel cusps with a uniform contact area of 0.384 mm2 served as antagonists in the chewing machine. Wear of the composites and enamel cusps, their combined wear, and the increase of the enamel contact surfaces were quantified. An increase in chewing pressure significantly enhanced the wear of both composite and enamel in all groups except for the antagonists opposing a HMC. The FPH was most wear-resistant to in vitro chewing pressures in the range of 6.58 to 19.74 MN/m2, the CPH at 26.32 MN/m2, while the HMC was the most enamel-friendly of the three composites tested. The FPH composite had the least disintegration in the occlusal contact area. The ranking of the composites generally varied at the different chewing pressures with respect to the three types of quantified wear--that is, composite wear, enamel wear, and total wear.

Acrylic Resins↗
PubMed1992

Effects of cement-curing modes on dentin bonding of inlays.

The aim of this in vitro study was to evaluate dentin adhesion after cementation of immediate direct "All Purpose" Hybrid (AP.H) composite inlays (Dentsply) and Cerec Dicor-MGC (Dentsply) inlays with the dentin adhesive Prisma Universal Bond 2 (Dentsply) and the dual-curing Dicor-MGC luting composite (Dentsply). In 24 extracted human molars, standard MOD cavities were prepared with one approximal margin located in enamel and the other one located in dentin. They were divided into four groups: (I) AP.H inlays, luting composite only, chemically cured; (II) AP.H inlays, luting composite, immediately-light-cured; (III) AP.H inlays, luting composite, initially chemically and delayed-light-cured (15 min); and (IV) MGC inlays, luting composite, initially chemically and delayed-light-cured (15 min). In vitro load cycles corresponding to five years of clinical stress followed. Initially and after specimens were loaded, the margins were analyzed quantitatively by SEM. The tooth/cement and cement/inlay interfaces were scored separately. The initial percentages of "continuous margin"--at both the tooth/luting composite and luting composite/inlay interfaces--were higher than 94% for all groups. At the end of the load cycles, the quality of the margins at the tooth/luting composite interface significantly decreased for all groups. The highest decrease was found for the cervical margins located in dentin, where only 37%-61% were scored as "continuous margin". The AP.H inlay/luting composite interface showed almost no change. At the MGC inlay/luting composite interface, the percentage of "continuous margin" decreased to 74%. After specimens were loaded, the percentage of "continuous margin" in dentin was lower than in enamel, despite the use of a dentin bonding agent (PUB 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Solubilization of the binding protein from Ehrlich ascites cells and erythrocytes to Pseudomonas aeruginosa cytotoxin.

The binding protein for pore-forming Pseudomonas aeruginosa cytotoxin was solubilized from Ehrlich ascites cell plasma membranes and rabbit and bovine erythrocyte ghosts using nonionic and zwittergent detergents. Analysis of solubilized plasma membranes from Ehrlich cells by a ligand-blot technique after separation by SDS-PAGE/electrophoretic transfer to nitrocellulose or affinity chromatography showed a protein of 70 kDa molecular mass, which binds to cytotoxin. The binding protein solubilized from rabbit erythrocyte ghosts showed a molecular mass of 50 kDa and that from bovine ghosts 55 kDa according to the former test. The binding proteins could be characterized as acidic. They contain a glycan moiety which is, however, not involved in the interaction of cytotoxin with the binding site.

ADP Ribose Transferases↗
PubMed1992

The importance of proximal curing in posterior composite resin restorations.

This in vitro study compared the marginal adaptation of enamel-bonded mesio-occlusodistal composite resin restorations placed using two different insertion techniques (one-step and two-step) and three different curing techniques (occlusal using opaque matrix and wedge systems and interproximal using transparent matrix systems and either transparent, non reflecting, or transparent, laterally reflecting wedges). The micromorphology of the enamel-restoration interface and the marginal seal were evaluated after the restorations were exposed to mechanical and thermal stresses. Although the difference was not statistically significant, the marginal quality of the restorations placed with the two-step technique was better than that of the restorations placed with the one-step technique. The restorations cured from the interproximal direction had significantly better marginal adaptation than did restorations cured only from the occlusal direction. The quality among the groups of interproximally cured restorations was not significantly different, because all the restorative techniques that were evaluated resulted in generally poor marginal quality.

Analysis of Variance↗
PubMed1992

Restoration quality in relation to wedge-mediated light channeling.

Thirty large mesio-occlusodistal cavities with their margins totally in enamel were restored using the three-sited light-curing technique in five different ways: group 1 = Mark I version of a light-reflecting wedge; groups 2 and 3 = interproximal curing with transparent, nonreflecting wedges; groups 4 and 5, Mark II version of the light-reflecting wedge with increased resiliency. In groups 3 and 5, the light that was not conducted by the transparent wedges was shielded by a piece of aluminum foil. It was found that, when used directly and unshielded, both Mark I and Mark II versions of the light-reflecting wedge induced significantly better marginal adaptation than the transparent, nonreflecting wedge, especially gingiovproximally. With both the nonreflecting and reflecting wedges, the shielding had no effect on the overall percentage of excellent margin. However, gingivoproximally, the shielding significantly improved the marginal quality in the nonreflecting wedge groups, leading to the conclusion that the first increment should be cured as thoroughly as possible from a gingivoproximal direction, preferably indirectly via light-conducting wedges. Direct irradiation from a lingual or buccal direction is less favorable.

Composite Resins↗
PubMed1992

In vitro evaluation of dentinal bonding agents in mixed Class V cavity preparations.

The effect of ten dentinal bonding agents on composite resin restorations was tested in mixed Class V cavity preparations. The marginal quality of the restorations was quantified under a scanning electron microscope before and after thermocycling. In addition, the marginal seal was semiquantitatively evaluated with a dye penetration technique. Marginal adaptation in dentin was poor in seven test groups. Three products showed values of excellent margin in dentin exceeding 50% after thermocycling. Furthermore, some dentinal bonding agents had a deleterious effect on marginal adaptation to the etched enamel surfaces.

Bicuspid↗
PubMed1992

[The effects of the processing technic on dentinal adhesion].

In this in vitro study, the effect of application techniques on marginal adaptation of thermal cycled class V restorations restored with an actual dentinal adhesive were quantitated using SEM and dye penetration. Under optimal application conditions, excellent results were generated: though a simple bulk insertion technique was used, no difference was found between enamel and dentin margins before and after thermal loading. On the other hand, contamination of the bonding agent with saliva before composite resin insertion dramatically decreased the percentage of "excellent margin" in dentin and in enamel. Similar effects were found after protecting the bonding agent with an insulating gel. No improvement in marginal adaptation was found after reapplication of the bonding agent. The class V inlay did not show better results than the direct filling technique. However, postcured inlays performed better than their non-postcured counterparts. Without etching enamel with a phosphoric acid gel, but by priming its surface, approximately 80% of "excellent margin" were found in enamel before thermal cycling. This percentage decreased significantly after thermal loading. Restorations totally confined to dentin had slightly lower percentages of "excellent margin" than the mixed class V fillings. The results of this study indicated, that by using dentinal adhesives, little changes and deviations from the correct procedure result in significant alterations in marginal adaptation.

Composite Resins↗